24 V AC Input Interface

[lbenson]

pilko--if you find yourself short of any standard components, send me a PM and if I have, I should be able to drop in the mail to you. Receiving shipments in Nova Scotia can sometimes be slow, I find. I brought my electronics-workshop-in-a-dufflebag (which has expanded to 3 dufflebags+), and have a more-than-lifetime supply of many things.

 

[pilko]

Ibenson--thanks for the offer. I mostly buy from Futurlec--great prices,but delivery sometimes up to eight weeks.

 

[jglenn]

If you can use a voltage input, it will be simpler than current sensing.

What I was talking about with the series input resistor, and 5.6V zener diode,

is a general clamp network that works for digital or analog inputs to a cpu.

Ignoring the opto for now, you know ESD and transients will take them out.

Just a R and a zener with the anode grounded. The band side goes to the chip input. You can slam 100V pulses in it, if your R is correct, with no damage.

Negative inputs are clamped to -.5V because the zener is also a normal diode
backwards. I have to solve damage problems on industrial eqpt, and this is one
method that prevents it, we use 5W TVS type zeners. Lightning still gets thru.

 

[pilko]

Thanks jglen info duly noted and will be testing later

 

[pilko]

Tested 24V AC input circuit as shown --- works fine.The graph is the input at the picaxe.